Sequencing the Arctic

March 1, 2013

1430

By David Smith

The Arctic has always been a mecca for biologists. In its extremes, the most magnificent species have flourished. And year after year, hardy scientists migrate from the cozy confines of university classrooms to the far North to study these amazing creatures. Chasing after caribou, tagging polar bears, filming the dive of an Eider duck, biologists have become part of the Arctic landscape. One of my favourite memories from school is of an old, silverback professor who would regale the class with adventure stories about his summers on Prince Patrick Island, Nunavut, where he explored the icy ocean for marine algae. He claimed that if it weren’t for his wife’s bad circulation, he’d have gladly spent all his days on the island.

But many of today’s polar researchers are trading in their parkas for lab coats. Arctic species, being on the frontlines of climate change, are prime targets for genome sequencing, which involves decoding the complete DNA sequence — the instruction booklet — of an organism. A lot of genomic bigwigs, including the United Sates Department of Energy, which helped sequence the human genome, and the National Research Council of Canada, have their eyes on the North. As you read this, teams of scientists are sweating away in stuffy computer labs, from Newfound land to California, deciphering the genetic code of the world’s coolest Arctic species.

Much of their focus is on the DNA from species inside permafrost — permanently frozen soil that spreads for thousands of kilometres across the Arctic. Permafrost is a hot topic because vast quantities of carbon are trapped within it. As Arctic temperatures rise, this carbon could leak from the frigid soils into the atmosphere, causing even sharper increases in global warming. The largest players in this equation are microscopic organisms living in and above the permafrost because they convert the sequestered carbon into greenhouse gases, like methane and carbon dioxide. But we still know very little about the types of microbes that call the permafrost home.

To better understand these tiny critters and their impact on climate, Canadian and US scientists are sampling the permafrost from diverse locations across the North, such as Ellesmere Island, Nunavut, and Hess Creek, Alaska. In a single gram of these samples there can be thousands of unique microorganisms, each with its own distinct genome. The researchers are indiscriminately sequencing DNA from the collected soils, trying to piece together like a jigsaw puzzle the genomes from these different microbes.

Early results from these experiments will make people shiver. A recent study published in the journal Nature by researchers from California found that some of the species inhabiting permafrost are, as expected, highly tuned machines for converting carbon into dangerous greenhouse gases. The study also showed that the microbial communities inside Arctic soils are extremely sensitive to thawing. Slight increases in temperature can cause rapid shifts in the number and types of species residing within permafrost, and could eventually lead to a proliferation of greenhouse-gas-generating organisms. As biologists learn more about permafrost biodiversity, they are eager to identify species that instead of dumping carbon into the atmosphere remove it. Depending on how common and hungry these taxa are, they may be able to offset some of the carbon footprint of their fellow microbial neighbours.

But it’s not all happening down in the dirt. Other researchers are taking advantage of genetic technologies to study polar algae — solar-powered unicells that flourish in the Arctic seas and melt water, and even in the ice and snow. Given that algae survive by sucking up carbon dioxide, they are just what the doctor ordered for counteracting global climate change. By unravelling the DNA sequence of these poorly studied photosynthesizers, biologists are hoping to learn about their biodiversity and how they may react to rising global temperatures. Their genomes could also give important insights into how species adapt to extreme habitats.

The Arctic environment is rapidly changing, as are the ways that scientists interact and under stand this environment. When we think of the North, we often picture big animals, like wolves, walruses and whales. But as with almost all of the Earth’s environments, it is the tiniest players — the bacteria, algae and other microorganisms — that determine the ultimate outcome.

David Smith is a Killam Postdoctoral Scholar in the Botany Department at the University of British Columbia, Vancouver.